The prescription medication gabapentin is available in generic form and as the brand-name drug Neurontin. It is primarily used for controlling seizures in people with epilepsy and to relieve the pain of postherpetic neuralgia, a condition that some people develop after they have shingles. Weight loss occurs infrequently as a side effect of this medication; weight gain is more likely to result.
Gabapentin is classified as an anticonvulsant. It helps control seizures by decreasing unusual excitement in the brain, and it relieves certain types of pain by changing how the body senses pain, explains PubMed Health. Gabapentin is structurally similar to the neurotransmitter gamma-aminobutyric acid, known as GABA.
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Weight Loss and Weight Gain
In clinical trials with adults and adolescents taking Neurontin involving about 4,700 participants, weight loss was an infrequent event, according to DailyMed. Weight gain was more likely, particularly in pediatric patients. A total of 1.8 to 2.9 percent of adolescents and adults in some clinical trials with Neurontin experienced weight gain. In one study with children aged 3 to 12 years, 3.4 percent gained weight while taking Neurontin, compared with 0.8 percent taking a placebo.
Digestive Side Effects
It is unclear why a small percentage of people lose weight when taking Neurontin, but it may be related to the small percentage who experience unpleasant digestive effects. In the studies highlighted at DailyMed, up to 5.7 percent of adult and adolescent participants experienced diarrhea, up to 3.9 percent nausea, up to 3.3 percent vomiting and up to 2.2 percent heartburn. In children ages 3 to 12, 8.4 percent experienced nausea, some with vomiting.
Neurontin is associated with many other side effects as well. You could experience constipation, drowsiness, weakness, dizziness, headaches, double or blurred vision, unsteadiness, anxiety and memory problems. An uncommon but serious side effect of antiepileptic drugs involves suicidal thoughts and behavior. About one in 500 adults and children during clinical studies with this type of medication became suicidal, notes PubMed Health.